Process for depilating hides and skins



Patented June 17, 1930 MAX nnnemuu, ornnusnnu; GERMANY H PROCESS FORDEPILATING HHJES AND SKINS I 170 Drawing Application filed July 27,1925, Serial No. 46,493, and in Germany February 12, 1925.'

The commonly employed means for removing the hair from hides and skins,such as lime-cream and other slackening means, for example mixtures oflime-cream and sodium sulfide, lime-creamand arsenic sulfide, lime-creamand sodium hydroxide, so dium sulfide alone, sodium hydroxide alone,sodium hydroxide" and enzymes, enzymes alone or other means forunhairing skins,

10 show theinconvenience that, at the same time as the produce thedepilation of the hides and shins, they damage the hair and thoseportions of the hide or skin from which the hair has been taken ofd". Inow have found that it is possible to avoid this inconvenience and toobtain nevertheless a perfectly satisfactory depilation oi the hides andskins it the hides and skins, prior to, the treatment with the commonlyused slackening means, or dressing means as lime,

lime and sodium sulphide, lime and arsenic sulphide, and the like, aretreated with substances which are also able to loosen the hair but donot injure the same. Substances 5 which are in first line suitable forthis purpose are inorganic and organic nitrogen bases as'ammonia,ethylene diamine, piperidine, pyridine and ureas, and thecompounds ofsaid nitrogen bases, as especially the sulphides of such nitrogen bases,and further soluble silicates, these substances being employedseparately or mixed with one another. I have found that, if the hidesand skins are-submitted to a treatment with solutions of the substancesmentioned separately or in mixture prior to the treatment with thecommonly used unhairing means, the hair or wool and the true skins orthe portions of the hides and skins from which the hair has been takenoil are not injured at all so that the value of the same is considerablyincreased. The leather made from skins and hides from which the hair hasbeen taken ed in this manner shows a fine, well adhering graincombinedwith good fullness and a special density without being rigid or brittle.

It has further been found that when the -hides and skins have beenpreliminarily with mixtures thereof the subsequent depilating processproper'canbe varried out in a fraction of the time which was hithertonecessary for the slackening process by means of lime-cream and thelike. en cleansing and working the hid with a mixture of lime-cream andsodium sulphideit is, for instance, possible to reduce by a preliminarytreatment of-the Mud described, the duration of the depilating processfrom 12 hours to half an hour. This efiect of the preliminary treatmentis very surprising and peculiar. The advantage resides not only in thereduction of duration of the depilating process proper but at the sametime in the very good preservation especially of the hair which resultsfrom the fact that the lime-cream or the like which impairs the hairacts upon the skin and hair only for a very short time. If the hides andskins prior to the action of one of the commonly used slackening meansare treated with solutions of ammonium sulphide or other ammoniaderivatives alone or in mixture with soluble silicates, so weakconcentrations of these solutions can be used that they do not cause aserious loosening of the hair, and only in combination with one of thecommonly used, subsequently applied slackening means they effectsufiieient depilation. A similar, altholfgh smaller effect is obtainedif the soluble silicates are applied alone. But these products mustalways be applied prior to r the tanning process proper if the desiredaction upon the true skin shall occur Examples 0 f application 1. Forunhairing or depilating a set of sheepskins or fleeces they are brought,after having been well soaked, into a solution which contains for onecubicmeter of water 4 10 liters of a technical-solution of ammoniumsulphide with a content of 10% (NH S, and they are left in this solutionfor one day. The skins are then put in anaqu'eous liquor which contains0,25 kilo of sodium sulphide for each cubicmeter of liquid and lime insuch a quantit that it will be well in excess of saturatlon of theliquid. After one hour theskins will release the hair, quite readily,and skins and hair are absolutely uninjured.

Instead of the indicated liquid for the preliminary treatment a solutionmay be 5 used'which contains for one cubicmeter of water liters of%ammonia. Instead of the liquid containing lime and sodium sulphide, anaqueous liquor containing 15 kilos of lime and 1.75 kilos of arsenicsulphide for each cubicmeter may be used for the unhairing process oralso any one of the other commonly used unhairing means may be employed.

2. For unhairing a set of calfskins they are brought into a solutionwhich contains for one cubicmeter of water 10 liters of a technicalammonium sulphide solution with a content of 10% (NHQ S and 10 liters ofcommercial water-glass solution of 38 to 40 B. So much of the liquid isused that the skins are well covered. After one day the skins are washedfor three hours in water which has to be renewed several times and theyare then brought. into an aqueous liquid mixture carrying 10% of limeand 1% of crystallized sodium sulphide. After one day, or at the utmosttwo days (according to the thickness of the skins), they will releasethe hair readily, hair and skins being .quite uninjured, and the leatherobtained after tanning possesses a well adhering grain andgreat-density.

For other hides and skins the process must be modified accordinglyalthough it remains principally the same.

Instead of ammonia or ammonia derivatives, suitable organic nitrogenbases and derivatives of the same may be used, as for instanceethylenediamine, piperidine, pyridine, urea substances and the like, orother mildly" acting hair-loosening means either alone or in mixture.

Having now particularly described and ascertained the natureof my saidinvention, I declarethat What I claim is: 1

1. A process for unhairing skins and hides which comprises firstlytreating the skins and hides with a watery solution containing anitrogen base readily soluble in water 5 while giving it an alkalinereaction, and

then with an alkaline unhairing means. 7

2. A process for unhairing skins and hides which comprises firstlytreating the skins and hides with a soluble compound containing anitrogen base readily soluble in water while giving it an alkalinereaction and then with an alkaline unhairing means.

3. A process for unhairing skins and hides which comprises treating theskins and hides with a mixture of compounds containing'a nitrogen basereadily soluble in water while giving it an alkaline reaction and withan alkaline unhairing means.

4. A process for unhairing skins and hides which comprises firstlytreating the skins gen base readily soluble in water while givng it analkaline reaction and then with an alkaline unhairing means.

5. A process for unhairing skins and hides which comprises firstlytreating the skins and hides with a basic derivative of ammonia which 1is readily soluble in water while giving it an alkaline reaction andthen with an alkaline unhairing means.

6. A process for unhairing skins and hides which comprises firstlytreating the skins and hides with a mixture containing a derivative of anitrogen base which is readily soluble in water "while giving it analkaline reaction, and an alkali metal silicate and thereafter with analkaline unhairing means.

7. A process for unhairing skins and hides which comprises firstlytreating the skins and hides with a mixture of" ammonium su lphide andan alkali metal silicate and thereafter with an alkaline unhairingmeans.

8. A process for unhairing skins and hides which comprises treating theskins and hides with a watery solution containing a nitrogen basereadily soluble in water while giving it an alkaline reaction and withan alkaline unhairing means. i

9. A process for unhairing skins and hides which comprises treatingskins and hides.

with ammonium sulphide and an alkaline unhairing means.

10. A process for unhairing skins and hides which comprises treating theskins and hides with a watery solution "of a basic derivative of ammoniareadily soluble in water while giving'it an alkaline reaction, a part atleast of the hydrogen of which is substi-- tuted by a hydrocarbon group,and with an alkaline unhairing means.

'l1- A process for unhairing skins and hides which comprises treatinskins and hides with ammonium sulphi e, and with a chemical slackeningmeans containing lime.

'12. A rocess for unhairing skins and hides WlllCh comprises firstlytreatin the skins and' hides with a mixture 0 ammonium sulphide and analkali metal silicate, and thereafter with a chemical slackening-meanscontaining lime.

In testimony whereof I have hereunto set my hand.

., DR. MAX BERGMANN.

and Hides with a basic derivative of a nitro- 7

